Apparatus and method for measuring thickness of tubings in downhole applications

Abstract

A magnetic flux measurement apparatus and method for nondestructive thickness imaging of metallic objects. The apparatus can primarily be used for thickness imaging of concentric metallic pipes, such as inner tubing and outer casing pipes in downhole applications. The magnetic flux measurement apparatus includes a transducer that includes a magnetic field source, magnetic flux sensor rings and a magnetic flux guide lens both positioned in alignment with a lateral axis of the magnetic field source. The magnetic flux guide lens is made of ferromagnetic material with high magnetic permeability that can direct flux lines into a predetermined sensor area for higher sensitivity and signal to noise ratio.

What is claimed is: 
     
       1. A magnetic flux measurement apparatus for nondestructive thickness imaging testing of metallic objects, the magnetic flux measurement apparatus comprises:
 a transducer comprising:
 at least one magnetic field source; 
 one or more magnetic flux sensor rings spatially positioned in alignment with a lateral axis of the at least one magnetic field source; and 
 a magnetic flux guide lens operably coupled to the at least one magnetic field source and passes through the one or more magnetic flux sensor rings in alignment with the lateral axis of the at least one magnetic field source, wherein the magnetic flux guide lens is of a tapered profile, wherein the magnetic flux guide lens has a proximal end and a distal end, the proximal end is coupled to the at least one magnetic field source, the magnetic flux guide lens tapers from the proximal end towards the distal end. 
 
 
     
     
       2. The magnetic flux measurement apparatus according to  claim 1 , wherein the at least one magnetic field source is a permanent magnet or an electromagnet. 
     
     
       3. The magnetic flux measurement apparatus according to  claim 1 , wherein the magnetic flux guide lens is coupled to a south or a north pole of the at least one magnetic field source. 
     
     
       4. The magnetic flux measurement apparatus according to  claim 1 , wherein the magnetic flux measurement apparatus further comprises a secondary magnetic field source spatially positioned geometrically at a predetermined distance away from the at least one magnetic field source in alignment with the lateral axis such that magnetic fields of the secondary magnetic field source and the at least one magnetic field source oppose each other. 
     
     
       5. The magnetic flux measurement apparatus according to  claim 1 , wherein each ring of the one or more magnetic flux sensor rings comprises:
 a body having evenly spaced apart magnetic flux sensors disposed throughout a periphery of the body in azimuthal direction for obtaining azimuthal spatial image measurements. 
 
     
     
       6. The magnetic flux measurement apparatus according to  claim 1 , wherein the one or more magnetic flux sensor rings are spatially positioned along the lateral axis with predetermined spacings among them. 
     
     
       7. The magnetic flux measurement apparatus according to  claim 1 , wherein at least two magnetic flux sensor rings of the one or more magnetic flux sensor rings that are adjacent to each other are oriented at a predetermined angular offset relative to each other for enhancing azimuthal resolution. 
     
     
       8. The magnetic flux measurement apparatus according to  claim 1 , wherein the magnetic flux guide lens is made of ferromagnetic materials with high magnetic permeability, the ferromagnetic material selected from a group consisting of iron, nickel, cobalt, and a combination thereof. 
     
     
       9. The magnetic flux measurement apparatus according to  claim 1 , wherein the magnetic flux guide lens is coupled to a north pole or a south pole of the at least one magnetic field source and is configured to guide magnetic field flux lines into a predetermined sensor area of the one or more magnetic flux sensor rings and aligning flux incidence angles in a radial direction. 
     
     
       10. A method for measuring thicknesses and thickness images of multiple concentric metallic pipes, the method comprises:
 providing a magnetic flux measurement apparatus, the magnetic flux measurement apparatus comprises: 
 a transducer comprising:
 at least one magnetic field source; 
 one or more magnetic flux sensor rings spatially positioned in alignment with a lateral axis of the at least one magnetic field source; and 
 a magnetic flux guide lens operably coupled to the magnetic field source and passes through the one or more magnetic flux sensor rings in alignment with the lateral axis of the magnetic field source, wherein the magnetic flux guide lens is of a tapered profile, wherein the magnetic flux guide lens has a proximal end and a distal end, the proximal end is coupled to the at least one magnetic field source, the magnetic flux guide lens tapers from the proximal end towards the distal end. 
 
 
     
     
       11. The method according to  claim 10 , wherein the at least one magnetic field source is a permanent magnet or an electromagnet. 
     
     
       12. The method according to  claim 10 , wherein the magnetic flux guide lens is coupled to a south pole or a north pole of the at least one magnetic field source. 
     
     
       13. The method according to  claim 10 , wherein the magnetic flux measurement apparatus further comprises a secondary magnetic field source spatially positioned geometrically at a predetermined distance away from the at least one magnetic field source in alignment with the lateral axis such that magnetic fields of the secondary magnetic field source and the at least one magnetic field source oppose each other. 
     
     
       14. The method according to  claim 10 , wherein each ring of the one or more magnetic flux sensor rings comprises:
 a body having evenly spaced apart magnetic flux sensors disposed throughout a periphery of the body in azimuthal direction for obtaining azimuthal spatial image measurements. 
 
     
     
       15. The method according to  claim 10 , wherein the one or more magnetic flux sensor rings are spatially positioned along the lateral axis with predetermined spacings among them. 
     
     
       16. The method according to  claim 10 , wherein at least two magnetic flux sensor rings of the one or more magnetic flux sensor rings that are adjacent to each other are oriented at a predetermined angular offset relative to each other for enhancing azimuthal resolution. 
     
     
       17. The method according to  claim 10 , wherein the magnetic flux guide lens is made of ferromagnetic materials with high magnetic permeability, the ferromagnetic material selected from a group consisting of iron, nickel, cobalt, and a combination thereof. 
     
     
       18. The method according to  claim 10 , wherein the magnetic flux guide lens is coupled to a north pole or a south pole of the at least one magnetic field source and is configured to guide magnetic field flux lines into a predetermined sensor area of the one or more magnetic flux sensor rings and aligning flux incidence angles in a radial direction.